Showing papers on "Dynamic range published in 1981"

A Voiceband Codec with Digital Filtering

Abstract: Oversampling and digital filtering have been used to design a per-channel voiceband codec with resolution that exceeds the typical transmission system requirement by more than 15 dB. This extended dynamic range will allow for the use of digital processing in the management of signal levels and system characteristics in many telecommunication applications. Digital filtering contained in the codec provides rejection of out-of-band inputs and smoothing of the analog output that is sufficient to eliminate the need for analog filtering in most telephone applications. Some analog filtering may be required only to maintain the expanded dynamic range in cases where there is a danger of large amounts of out-of-band energy on the analog input impairing the dynamic range of the modulator. The encoder portion of the oversampled codec comprises an interpolating modulator that samples at 256 kHz followed by digital filtering that produces a 16-bit PCM code at a sample rate of 8 kHz. In the decoder, digital processing is used to raise the sampling rate to 1 MHz prior to demodulation in a 17-level interpolating demodulator. The circuits in the codec are designed to be suitable for large-scale integration. Component matching tolerances required in the analog circuits are of the order of only ± 1 percent, While the digital circuits can be implemented with fewer than 5000 gates with delays on the order of 0.1 μs. In this paper the response of the codec is described mathematically and the results are confirmed by measurements of experimental breadboard models.

Interferometric spectrum analyzer.

Abstract: Dynamic range is a key performance parameter for spectrum analyzers. The dynamic range of a Bragg cell power spectrum analyzer is generally limited by the dynamic range of self-scanned photodetector arrays. Interferometric techniques can be used to increase the dynamic range; but it is at the expense of increasing the number of photodetectors required, when the interference is introduced in the spatial domain, or a large photodetector bandwidth, when the interference is introduced in the temporal domain. In this paper we describe an interferometric approach wherein a second Bragg cell generates a spatially modulated reference waveform to produce an interference term that has a constant temporal frequency for all spatial frequencies. The advantages of this approach are lower photodetector bandwidth, improved dynamic range, improved cross talk suppression, more efficient use of the Bragg cell time–bandwidth product, immunity to scattered noise, and improved short pulse detectability. The chief disadvantage is the need for a discrete element photodetector array; when such arrays become available in hybrid or integrated packages, an additional advantage will be that of parallel postdetection processing.

Multimode fiber-optic hydrophone based on a schlieren technique

Abstract: A multimode fiber-optic hydrophone is described which is based upon a schlieren acoustooptic intensity modulation mechanism. Computer modeling of critical device parameters was experimentally verified and used to indicate ultimate attainable device performance. The device was shown to be able to detect the Knudsen noise level for frequencies up to 1 kHz, to have a dynamic range of 125 dB, to have an omnidirectional receiving response, and to be able to detect displacements as small as 3.4 × 10−3 A. The device is not susceptible to phase noise, is relatively insensitive to static pressure head variations and is electrically passive.

Dynamic volume expander varying as a function of ambient noise level

Abstract: To provide for response of audio reproduction equipment with the full dynamic level range, for example of music, intended by a composer, although radio signals transmitted have been compressed to reduce the signal-noise level, an expander circuit (20a, 20b, 20c) is activated based on ambient noise level conditions as sensed, for example, by a microphone (12) which determines the ambient noise level. If the ambient noise level, for example within certain frequency bands, as selected by filters (32a, 32b, 32c) is low, so that the full dynamic range (difference between low volume and high volume passages) can be reproduced, a range expander (20a, 20b, 20c) is controlled, for example within selected frequency bands, to reproduce the respective frequencies, or the overall signal, with a dynamic range greater than that of the received compressed signal and, preferably, corresponding to the dynamic range of the original signal which was then compressed for transmission. To prevent a microphone from responding not only to ambient noise but also to the reproduced program, the reproduced program level can be sensed, for example, by an amplitude detector (14a) and, when the reproduced program level is low, briefly entirely interrupt the program level while activating the microphone to sense then ambient noise level and, if the sensed ambient noise level is low, thus permit control of the dynamic range expansion circuitry to expand the dynamic range of the reproduced signal to improve listening conditions.

A flexible, computer-controlled video microscope capable of quantitative spatial, temporal, and spectral measurements.

Abstract: A video microscope system has been constructed and tested that incorporates computer-controlled video cameras for high-resolution and low-light microscopy. The low-light camera system involves a dual microchannel plate-image intensifier capable of photon gain as high as 500 000 and a gated silicone-intensified target vidicon to achieve usable photon sensitivity with a noise equivalent signal of only 2 photons (500 nm) per pixel per second. We have compared the limitations and capabilities of this camera system with those of a high-resolution video camera and conventional photomicroscopy. Uses of the low-light camera coupled to a computer system include image acquisition of weak-light images from self-luminous specimens, fluorescence microscopy with weak exciting light, kinetic resolution of calcium-mediated events as monitored by the calcium-sensitive bioluminescence of aequorin, and spatially resolved spectroscopic measurements. Flexible use of this system in these various applications is possible because it allows operation with illumination intensities over a dynamic range of 100 000:1.

A programmable transversal filter for voice-frequency applications

Abstract: A fully integrated, programmable transversal filter optimized for low-noise, low-power, voice-frequency applications is described. The filter, fabricated with a standard double-poly NMOS process, achieves convolution of an analog input signal with digital tap weightings using a structure with sample-and-hold gates for analog storage and a multiplexed MDAC for multiplication. The design of the filter eliminates fixed pattern noise usually associated with such structures and enables a dynamic range in excess of 70 dB (LPF, f/SUB o//f/SUB s/=0.08) to be achieved at an 8 kHz sampling rate with a power dissipation of less than 80 mW. This area efficient device forms the basis for a range of possible voice-band signal processing functions.

A CMOS digitally controlled audio attenuator for Hi-Fi systems

Abstract: Describes an audio attenuator designed for use in digitally controlled Hi-Fi systems. The circuit is fabricated with a thin film on CMOS process and has a dynamic range of 0 to -88.5 dB in 1.5 dB steps. Total harmonic distortion for the complete circuit is typically -87 dB and wide-band signal/noise ratio is typically -86 dB.

Performance of integrated dynamic MOS amplifiers

Abstract: The letter presents measured data of two different types of dynamic amplifier which have been integrated in a standard CMOS metal gate technology. For a supply voltage of ±5 V, gains of 70 dB were obtained with a power dissipation of 58 μW and 500 μW at clock frequencies of 10 kHz and 100 kHz, respectively. The dynamic range exceeds 100 dB.

Texas Instruments (TI) 800X800 Charge-Coupled Device (CCD) Image Sensor

Abstract: Very-large area high-performance CCD image sensors with 800 x 800 pixel format have been successfully fabricated and operated on the basis of a three-level polysilicon gate technology. They are thinned to 8 microns over the entire 12.2 x 12.2 mm active area, and are used in the rear illumination mode. The light transfer characteristic has a gamma value of 1.000 + or - 0.002 over most of the dynamic range. Analysis of the noise behavior shows that the device SNR is shot-noise-limited over most of the dynamic range. Simple on-chip signal processing can be performed using an integration well to noiselessly collect signal charge from multiple pixels prior to reading out the charge. A UV-sensitive phosphor has been applied to the chip, yielding a device capable of imaging at wavelengths from the vacuum UV to the near IR.

High‐performance cryogenic pulsed NMR spectrometer

Abstract: A pulsed NMR spectrometer for cryogenic use is described. It includes an improved coupling scheme which is suitable for installation in most cryostats. An rf preamplifier has been developed which offers wide bandwidth, high gain, low noise and fast recovery (⩽2 μs). While the spectrometer was designed for a resonance frequency of 27 MHz, extension from 4–100 MHz is discussed. At 27 MHz the bandwidth of the free‐induction decay is 1 MHz, and the dead time, after the end of the rf pulse, is 3.6 ms. Techniques are presented for reducing the dead time, the noise, and the amplitude of ground loops as well as extending the signal bandwidth and dynamic range.

A modular signal processor for digital filtering and dynamic range control of high quality audio signals

Abstract: A high speed, low cost digital signal processor has been designed and built suitable for real-time operation on high quality audio signals. The machine is microprogrammed and so is potentially a hardware solution to many signal processing problems. The paper describes its application to audio equalisation and dynamic range control of a kind found in a range of broadcast and studio equipment. The reasons for the choice of filter structures and a method for dynamic range control are discussed with particular attention to the wordlengths required. The features of these structures are incorporated in a modular, hardware-efficient design which can be expanded to a large system under common control.

Circuit arrangements for modifying dynamic range

Abstract: Improvements in compressors, expanders and noise reduction systems are disclosed which reduce the susceptibility of such circuit arrangements to undue control by signals outside the pass-band(s) (i.e., stop-band signals) in which the circuits are active. Level dependent circuitry operates, particularly by means of non-linear processing, to reduce the circuit response to the effect of stop-band signal components at high input signal levels.

Signal processing circuitry for a distance measuring system

Abstract: For a distance measuring system in which a light measuring arrangement responds to changes in light to establish distances, a processing circuit includes a quasi-compression device that receives the electrical signal from the light measuring arrangement and maintains the normal gain of an amplifier to amplify the electrical signal when the electrical signal is low. The compression device reduces the amplifier gain when the electrical signal is higher. This narrows the dynamic range necessary for the distance measuring system.

Third-octave analysis of multichannel amplitude compressed speech

Abstract: Multiband amplitude compression has been studied as a compensation for the reduced auditory dynamic range often associated with sensorineural hearing loss, since it is capable of altering the dynamic range of speech as a function of frequency. Compression systems are generally characterized by their response to steady state tones and to simple dynamic stimuli, such as tone bursts. Level distributions of unprocessed and compressed materials are presented to demonstrate that these descriptions are inadequate to predict the processing of speech. A simple analysis of multiband compression which incorporates the interactions of static and dynamic properties is presented.

Large conversion efficiency and dynamic range for sis mixers

Abstract: Large but finite conversion gain with positive output impedance is predicted for a single sideband SIS mixer at zero temperature. It is found that an optimum occurs for small local oscillator power, unlike the classical case. Still, the dynamic range can be quite large. Fundamental limits allow a dynamic range in excess of 70 dB for Pb-alloy junctions with a 500 MHz bandwidth.

Spectrometer with electronic readout for CO2 lasers

Abstract: The spectrometer uses an array of 50 pyroelectric detectors etched from a PVF2 sheet in the precise positions for the various lines in the P and R branches of the CO2 spectrum. The detectors are accessed in sequence to give a bar chart display of the spectrum. Compared to the conventional spectrum analyser (using a phosphor screen for CW or a graphite screen for pulsed lasers) the instrument gives a substantial advantage in sensitivity with a noise equivalent power of 100 mu W for CW or 200 nJ for pulsed. The dynamic range is 3000:1, enabling the detection of weak satellite lines, while a digital store allows monitoring of each shot of an inconsistent but low repetition rate laser.

An analysis of errors in wave digital filters

Abstract: The roundoff noise properties of wave digital filters realized with fixed-point arithmetic are studied. The dynamic range of these filters is considered and the effects of scaling on the roundoff noise are deternined. Claimns have been made in the literature concerning the favorable coefficient sensitivity properties of wave digital filters. It is shown that specific configurations of wave digital irdters do exhibit favorable coefficient sensitivity properties, and that filters can be realized winch are insensitive to overall coefficient error at zero frequency (low pass).

Broad-band high-speed microwave power sensor using hot carriers in semiconductor

Abstract: The principal characteristics of a semiconductor power sensor based upon the temperature rise of hot carriers are investigated. A method of designing a broad-band coaxial mount is described. The hot-carrier power sensor is fabricated by a whisker contact to p-type germanium. A sensor using optimum resistivity results in a noise equivalent power of -58 dBm/Hz1/2 with a 60-dB dynamic range. A broad-band-matched mount, having an average VSWR of 1.1:1 was attained for the frequency range from 1 to 12 GHz.

Digital frequency control circuit

Abstract: PURPOSE:To widen the dynamic range of a broadcast transmission or recording and reproduction system, by obtaining a simple frequency control circuit of digital circuit constitution that includes complementary HPF and LPF. CONSTITUTION:HPF6 and LPF7 are complementarily provided and coefficient units 4 and 5 are controlled by a coefficient-unit control circuit. Coefficient-unit control circuit 9 detects which of the high frequency component and low frequency component of an input signal is high in level; when the level of the high frequency component exceeds a certain value, the coefficient of coefficient unit 4 is decreased and when the level of the low frequency component exceeds the certain value, the coefficient of coefficient unit 5 is decreased. Consequently, the input signal large in dynamic range can be compressed without deteriorating its sound quality much and the signal is transmitted by use or a transmission line, whose dynamic range is restricted, without being clipped, so that the dynamic range can be increased.

Large Time-Delay-And-Integration (TDI) Arrays And Focal Plane Structures With Intrinsic Silicon Response

Abstract: This paper is primarily a review of two recent focal plane development projects. The first focal plane consists of six 1024x64 element TDI image sensor chips mounted on a prism beam-sharer. This focal plane is designed to give a video signal with high SNR over a wide dynamic range. The second focal plane consists of a single 1024x128 element TDI image sensor chip. It is designed to perform over a wide dynamic range extending down to starlight scene illumination levels. Both chip designs employ buried channel, silicon gate CCD technology. The silicon gate sensing area is designed for maximum broadband quantum efficiency over the range 500-900nm; an average quantum efficiency over that range of 50 percent has been achieved. The sensor element in both chip designs is a 20x20 micrometer square stage of a four-phase CCD register. This element design provides high MTF and a saturation charge level of approximately 1x106 electrons/pixel as is needed for achieving high SNR. On-chip preamplifiers are designed for specific requirements of the focal planes. The chip for the first focal plane utilizes a highly linear resettable floating gate amplifier; the linearity facilitates matching of imagery generated by neighboring chips. The chip for the second focal plane has two preamplifiers which may be read out in parallel; the first handles the full dynamic range of the CCD output and the second, because of higher gain, handles only the low end of the CCD output. The high gain amplifier has operated at 1MHz sample rate with a noise equivalent signal level of approximately 20 electrons/pixel RMS.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wideband Interferometric Acoustooptic Bragg Cell Spectrum Analyzer

Abstract: The experimental results on interferometric Bragg Cell Spectrum Analyzer are indeed encouraging. An experiment was performed using a 5 mW HeNe laser in Mach-Zehnder interferometric Configuration. A linear chirp was used to generate the reference beam. We were able to obserw58 dB Dynamic Range for CW and 54 dB DR for 5ps pulsed signals with 100% Probability of Intercept and less than 1 ps Time of Arrival accuracy. Pseudo Noise Sequence was a lso tried in another experiment with good results at reduced system bandwidth.

Automatic component meter range design using floating-point conversion

Abstract: The control of dynamic range and resolution in the conversion of the voltage and current signals on whose measurement depends the operation of a modern electronic component meter or 'bridge' is a major problem in design The paper presents a modified form of dual-slope analogue-to-digital convertor for this purpose Called adaptive acquisition time (AAT) conversion, the technique directly produces a floating-point binary output representation of the signal for subsequent computation purposes The AAT convertor leads to a bridge range design procedure resulting in a maximum variation of convertor counts of only 21 over the entire resistance range of the instrument from 05 - to 8 M- The design of the excitation circuit resulting from the use of AAT conversion itself leads to an autoranging system faster in operation than conventional step-by-step methods A technique for reducing the sensitivity of the integrator to timing errors in the acquisition period when unfiltered signals

Guided Wave Optical RF Spectrum Analyzer

Abstract: The design, fabrication and performance of an integrated optical R.F. spectrum analyzer is described. The device consists of an injection laser, the IO substrate and a photodiode array. It operates over a frequency band-width of 400 MHz centered at 600 MHz and with a complete frame time of 2 mu sec. An R. F. input signal dynamic range in excess of 20 dB has been measured.

Magnetic recording reproducing system

Abstract: PURPOSE:To expand the dynamic range of a record reproducing signal, by reproducing a compressed data which is recorded together with a compressed signal, and expanding a reproducing compressed signal complementarily with its compression. CONSTITUTION:A compressed data of specific frequency which is recorded together with a compressed analog signal of the dynamic range, in the cassette tape is reproduced, it becomes a binary control signal through the filter 14 and the A/D converter 15, and gain of the amplifier 16 is controlled. Accordingly, the dynamic range is expanded complementarily with its compression, a reproducing signal becomes satisfactory in its frequency characteristic, and comparing with the dynamic range which is not subjected to the compressing and expanding processing, the record reproduction of the dynamic range is further expanded.

Wide dynamic range pulse to pulse rate converter

Abstract: A system for converting a variable pulse rate input signal to an analog output signal responsive to the rate of the input A plurality of parallel channels are utilized in the conversion process, each covering a different portion of the desired dynamic range of the system, with the outputs superpositioned in a weighted fashion for producing a combined output

Linear dynamic range of an optical nearfield diffraction technique for studying ultrasonic waves

Abstract: An optical nearfield diffraction technique was recently described for studying ultrasonic waveforms in the low megahertz frequency range [W. A. Riley, J. Acoust. Soc. Am. 67, 1386–1388 (1980)]. The theoretical optical amplitude response of this technique is linear with acoustic pressure under only a limited range of experimental conditions. The objective of this work was to experimentally determine the linear dynamic range of this optical system assembled from inexpensive components and used in conjunction with a good laboratory oscilloscope. A linear dynamic range of approximately 20 dB was determined from these results which corresponds to acoustical powers between 0.1 and 10 mW in distilled water. This 20‐dB window can be lowered approximately 10 dB by selecting an acousto‐optic medium more efficient than water. It can be raised by 40 dB by examining normal reflections from the boundary between liquids having small acoustic impedance differences. With this approach, one can effectively observe narrow‐band acoustic pulse waveforms over a 70‐dB dynamic range from approximately 10 μW to 100 W with a precision of approximately 1 dB.

Analysis and design of a broadband delta modulation system

Abstract: A simple treatment is provided of the analysis of an adaptive delta modulation system for evaluating the performance of the system in terms of complexity, signalto- noise ratio and dynamic range. The analysis assumes a simple adaptation algorithm and a normal density function input signal with flat spectrum.A brief description of the implementation of the system is given and finally the experimental results are compared with the theoretical results.